This invention relates to oligomeric bischloroformic acid esters which are obtainable, in a two-phase reaction, from selected cycloaliphatic bisphenols and other bisphenols by introducing phosgene.
Bischloroformic acid esters are suitable as educts for the production of cyclic polycarbonate compounds (as a precursor for high-molecular polycarbonates in accordance with DE 19 636 539) and of linear polycarbonates, for example, from solution polymerisation.
The bisphenol 1,1-bis(hydroxyphenyl)-3,3,5-trimethylcyclohexane (TMC bisphenol) produces polycarbonates having a high glass temperature. Polycarbonates having a lower glass temperature are often required, because of their better workability.
Suitable compounds are, for example, copolymers with other bisphenols.
It is in principle possible to mix an oligomeric bischloroformic acid ester precursor of TMC bisphenol (precursor 1; V1) with another oligomeric bischloroformic acid ester precursor (precursor 2; V2) prior to the reaction. But a statistical sequence of the monomeric bisphenols (V1) and (V2) is not then obtained during the subsequent reaction, and blocks of precursor 1 and precursor 2 are formed instead. For this reason it is desirable to prepare oligomeric bischloroformic acid ester precursors which are themselves built up statistically from TMC bisphenol and other bisphenols.
The invention accordingly provides mixtures of bischloroformic acid esters corresponding to formulae (I), (II) and (III) 
wherein
R1 and R2 independently of one another denote hydrogen, halogen, preferably chlorine or bromine, C1-C8-alkyl, C5-C6-cycloalkyl, C6-C10-aryl, preferably phenyl, and C7-C12-aralkyl, preferably phenyl-C1-C4-alkyl, in particular benzyl,
m is an integer from 4 to 7, preferably 4 or 5,
R3 and R4 independently of one another denote hydrogen or C1-C6-alkyl and
X denotes carbon,
with the proviso that, on at least one X atom per repeat unit in (I) or (III), R3 and R4 simultaneously denote alkly,
Z is an aromatic group having 6 to 30 C atoms and can contain one or more aromatic nuclei, can be substituted and can contain aliphatic groups or cycloaliphatic groups which differ from the cycloaliphatic groups in (I), or hetero atoms as bridge-type cross-links,
p, q, r and s represent a natural number from 1 to 15 and the molar ratio of the cycloaliphatic bisphenol units to the aliphatic bisphenol units is 1:10 to 10:1.
Z is preferably 
wherein Me=methyl group.
The mixtures of bischloroformic acid esters are preferably prepared by introducing phosgene into a mixture of bisphenols corresponding to formulae (IV) and (V) in the molar ratio of 1:10 to 10:1
in a two-phase system consisting of water and an organic solvent, preferably methylene chloride, at xe2x88x925xc2x0 C. to 40xc2x0 C., the pH value of the aqueous phase being maintained at between 1 and 13, preferably between 2 and 9,by the addition or previous provision of an alkali metal hydroxide or alkaline-earth hydroxide.
Here X, R1, R2, R3, R4 and m have the meanings given for formula (I).
Preferably on 1 to 2 X atoms and in particular on only one X atom per molecule (IV), R3 and R4 simultaneously denote alkyl.
The preferred alkyl group is methyl. The X atoms in the a-position to the diphenyl-substituted C atom (C-1) are preferably not dialkyl-substituted, but alkyl disubstitution is preferred in the xcex2-position to C-1.
Dihydroxydiphenylcycloalkanes having 5 and 6 C atoms in the ring in the cycloaliphatic group (m=4 or 5 in formula (IV)) are preferred, for example, the diphenols corresponding to formulae (IVa) to (IVc) 
wherein 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (formula (IVa) with R1 and R2 denoting H) is particularly preferred. The polycarbonates can be produced from diphenols corresponding to formula (I), in accordance with the German Patent Application P 3 832 396.6.
For the repeat units, other diphenols, for example, corresponding to formula (V)
HOxe2x80x94Zxe2x80x94OHxe2x80x83xe2x80x83(V)
are used in addition to the diphenols corresponding to formula (IV). Suitable diphenols corresponding to formula (V) are those wherein Z is an aromatic group having 6 to 30 C atoms and can contain one or more aromatic nuclei, can be substituted and can contain aliphatic groups or cycloaliphatic groups other than those corresponding to formula (I) or hetero atoms as bridge-type cross-links.
Examples of diphenols corresponding to formula (V) are: hydroquinone, resorcinol, dihydroxydiphenyls, bis(hydroxyphenyl)alkanes, bis(hydroxyphenyl)cycloalkanes, bis(hydroxyphenyl) sulfides, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl) ketones, bis(hydroxyphenyl) sulfones, bis(hydroxyphenyl) sulfoxides, xcex1,xcex1xe2x80x2-bis(hydroxyphenyl)diisopropylbenzenes as well as ring-alkylated and ring-halogenated compounds thereof.
Preferred diphenols are xcex1,xcex1xe2x80x2-bis(hydroxyphenyl)-m-diisopropylbenzene, xcex1,xcex1xe2x80x2-bis(hydroxyphenyl)-p-diisopropylbenzene and 2,2-bis(4-hydroxyphenyl)propane; xcex1,xcex1xe2x80x2-bis(hydroxyphenyl)-m-diisopropylbenzene and 2,2-bis(4-hydroxyphenyl)propane are particularly preferred.
These and other suitable diphenols are described, for example, in the monograph: H.Schllell. xe2x80x9cChemistry and Physics of Polycarbonatesxe2x80x9d, Interscience Publishers, New York. 1964.
Mixtures of bisphenols (V) and of other bisphenols may, of course, also be used as cobisphenols.
For this, examples of other preferred bisphenols are: 4,4xe2x80x2-dihydroxydiphenyl, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)cyclohexane, xcex1,xcex1xe2x80x2-bis(hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, bis(3,5-dimethyl-4-hydroxyphenyl)methane, 2,2-bis(3,5-dimethyl-4-hydroxy-phenyl)propane, bis(3,5-dimethyl-4,4-hydroxyphenyl) sulfone, 2,4-bis(3,4-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane and 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane.
Compounds used as bisphenols corresponding to formula (IV) are preferably 1,1-bis(hydroxyphenyl)-3,3,5-trimethylcyclohexane or 1,1 -bis(hydroxyphenyl)-3-methylcyclohexane, particularly preferably 1,1-bis(hydroxyphenyl)-3,3,5-trimethyl-cyclohexane.
Compounds used as bisphenols corresponding to formula (V) are preferably 2,2-bis(hydroxyphenyl)propane (BPA), 1,1-bis(hydroxyphenyl)ethane or 2,2-bis(hydroxyphenyl)butane, particularly preferably 2,2-bis(hydroxyphenyl)propane.
The invention also provides the use of the mixtures of bischloroformic acid esters according to the invention for the production of cyclic cooligocarbonates.
The synthesis of the cyclic cooligocarbonates is carried out by synchronous addition of the solution of the mixtures of bischloroformic acid esters in methylene chloride and of 3 to 15 mol. % of an organic amine, preferably triethylamine, to a two-phase mixture of methylene chloride and water, during which the pH value of the aqueous phase is maintained at between 7 and 13, preferably between 9 and 11,by the addition or previous provision of an alkali metal hydroxide or alkaline-earth hydroxide, and the temperature is 0xc2x0 C. to 40xc2x0 C., preferably 30xc2x0 C. to 40xc2x0 C. If necessary, in addition up to 10 mol. % of other bisphenols are added.
The invention also provides the use of the mixtures of bischloroformic acid esters according to the invention for the production of linear statistical copolycarbonates.
The high-molecular polycarbonates obtained from the bischloroformic acid esters according to the invention, optionally in combination with other bischloroformic acid esters, can be produced by the known processes for polycarbonate production, preferably by the phase interface process (cf. H. Schnell, xe2x80x9cChemistry and Physics of Polycarbonatesxe2x80x9d, Polymer Reviews, Vol. IX, page 33 ff., Interscience Publishers, 1964.)
The synthesis of the linear statistical copolycarbonates is carried out, for example, by a two-phase reaction of a solution of the mixtures of bischloroformic acid esters in methylene chloride with inorganic bases, preferably alkali metal hydroxides, dissolved in water, at a pH value of 7 to 13 and at a temperature of 0xc2x0 C. to 40xc2x0 C. in the presence of 0.01 to 2 mol. % of an organic amine, preferably triethylamine or N-ethylpiperidine, with 0 to 80 mol. % bisphenols corresponding to formulae (IV) and (V) and 0 to 7 mol. % monophenols possibly being added.
Monofunctional compounds in conventional concentrations are used as chain stoppers for the known per se control of the molecular weight of the polycarbonates. Suitable compounds are, for example, phenol, tert. butylphenols or other alkyl-substituted phenols. In particular, small quantities of phenols corresponding to formula (VI) 
wherein
R denotes a branched C8- and/or C9-alkyl group are suitable for controlling the molecular weight.
In the alkyl group R the proportion of CH3 protons is preferably between 47% and 89% and the proportion of CHxe2x80x94 and CH2, protons is preferably between 53% and 11%; equally preferably, R is in the o- and/or p-position to the OH group, and particularly preferably the upper limit of the ortho proportion is 20%. The chain stoppers are generally used in quantities of from 0.5 to 10 mol. %, preferably 1.5 to 8 mol. %, based on diphenols used.
The copolycarbonates obtained have neither block-type nor alternating structures. They are built up statistically.